The use of deep eutectic solvents as a promising approach in the design of microwave-based green gas sensors

Abstract

This study investigates a new kind of sensitive layer composed of choline chloride–urea deep eutectic solvent for microwave gas sensor application to detect HCl vapor. The sensing microwave device is based on a quarter-wavelength stub resonator operating in C-band with its gap filled with the sensitive layer. Accordingly, the microwave response of such a device depends on its exposure time to HCl vapor. Furthermore, the dielectric characteristics (ε_r and tgδ) of the sensitive layer and their variation related to HCl vapor exposure have been retrieved and checked through another microwave device specifically developed, namely a 50 Ω transmission line with a gap.